% In fluid dynamics, the Darcy friction factor formulae are equations – based
% on experimental data and theory – for the Darcy friction factor. The Darcy
% friction factor is a dimensionless quantity used in the Darcy–Weisbach
% equation, for the description of friction losses in pipe flow as well as
% open channel flow. It is also known as the Darcy–Weisbach friction factor,
% resistance coefficient or simply friction factor and is four times larger
% than the Fanning friction factor.

% f is the Darcy friction factor
% Roughness height, epsilon (m, ft)
% Hydraulic diameter, D (m, ft) – For fluid-filled, circular conduits, D = inside diameter
% Re is the Reynolds number
% densiity of fluid rho
% viscosity of the fluid miu